Device for dispensing thixotropic materials

ABSTRACT

A fluid dispenser for use in consistently depositing relatively thick and lumpy materials onto receiving surfaces which employs a supply path to a plurality of pump/valve combinations and a feedback pressure line to assure an adequate pressure at the point of deposit. There are positive displacement pumps which operate continuously through the plurality of valves with an additional feedback path to assure constant flow of the material.

This application is a continuation of application Ser. No. 08/260,555,filed Jun. 16, 1994, now U.S. Pat. No. 5,445,674 which is a continuationof application Ser. No. 07/847,944, filed Mar. 6, 1992, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to fluid dispensers and more particularlyto dispensers for relatively thick mixtures such as sauces for foodssometimes containing lumps. The invention finds particular utility indispensing materials such as tomato sauce onto pizza crusts in anassembly line production where a plurality of pizza crusts are caused tomove past the dispenser and to have an fixed amount of tomato saucedistributed over their surface.

2. Description of the Prior Art

Examples of dispensers presently known in the art may be seen in, forexample, U.S. Pat. No. 3,602,154 issued Aug. 31, 1971 to E. H. Schimkatet al. Such devices employ a supply tank which feeds the food productssuch as pizza sauce to a plurality of pistons which force the sauce intoa plurality of valves located above a dispensing area. A conveyor beltmoves the pizza crusts to the dispensing area and the pizzas are thenlifted and rotated underneath the valve to apply the sauce thereto. Suchapparatus is extremely difficult to manage, has no ability to easilychange the size of the pizzas being processed and requires that thepizzas be evenly placed on the conveyor system at known location inorder to operate properly.

The assignee of the present invention has devised a system in which thepizzas may moved under a dispensing area past a plurality of detectorswhich sense their presence and a signal is provided to a computer whichalso receives an input indicative of the speed of the conveyor andaccordingly knows the moment that the leading edge of the pizza crustarrives in a dispensing area. The computer controls the opening of theappropriate valves as the pizza crust moves through the dispensing areaso that the sauce from the tank is pumped through one or more orificesand onto the crusts for the length of time necessary to lay a pluralityof strips thereon. As the pizza crust moves out of the dispensing area,the appropriate valves are closed and thereafter the strips of saucetend to flow together as the crust continues to move so as to leave arelatively even surface of sauce thereon.

Systems such as described above have encountered a number of problemsparticularly when the fluid is a tomato sauce to be dispensed onto anobject such as a pizza crust. For example, tomato sauce is known to actin a thixotropic manner; that is having a tendency to resist flowinguntil it is agitated to start. Accordingly, low flow usually occurs uponstarting and uneven flow of sauce to crust results. The importance ofthis is found in fact that previous systems require a 20% or more excesstarget flow to assure at least a predetermined quantity of sauce isprovided to each pizza. Not only is the extra cost of sauce significantbut inconsistent pizzas result. It has been found that the pizzas whichhave excess sauce variation do not meet customer expectations of auniform product. Accordingly, it is extremely desirable to provide sauceto the pizzas in a consistent manner.

Another problem encountered in prior art systems is blockage in one ormore nozzles because of the fact that the sauces being dispensed maycontain particles of spice or tomato. When this occurs, a number ofpizza crusts may have one or more strips of sauce missing before anoperator notices the discrepancy and corrects the blocked valve byapplying an excess pressure thereto to blow the blockage away. Becauseof this, time has been wasted and several pizza crusts have to bediscarded. To minimize this problem, the prior art has needed to havelarger than desirable valve nozzles and this has produced a poor spreadof sauce.

Another difficulty encountered in the prior art arises when there isinsufficient pressure to assure continuous full flow conditions. Whenthis occurs, one or more of the valves do not receive enough sauce anduneven and inconsistent applications result.

Prior art dispensing systems have also been unable to handle differentset-up arrangements and can handle only one pizza size at a time. It isdesirable to be able to sometimes use a single lane, sometimes two andsometimes three or more lanes and to handle different size crusts(5,7,9,11 & 12 inch pizzas are common) without having to change thevalve positions.

SUMMARY OF THE INVENTION

The present invention while useful in various sorts of dispensers willbe described in the embodiment where a tomato sauce is dispensed ontopizza crusts. In the present invention an improved dispenser is providedwhich overcomes the problems encountered in the prior art. Continuousflow to the valves is assured by providing a by-pass flow path throughwhich a portion of the flow always occurs and accordingly, the initialflow problem with a "thixotropic" material does not occur. Also, backpressure is provided in the bypass path to provide a reverse pressureand assure that the sauce is always under sufficient pressure to themetering pumps. A unique positive displacement pump utilizing non-foodcontaminating materials such as stainless steel is provided which feedsthe flow to the valves in a manner which tends to prevent blockage inthe valves and, if blockage does occur, the pressure in that line buildsup to blow it free because each nozzle has its own pump. Also, in thepresent invention, the valves are opened and closed by a computer insuch a manner that any combination of them may be employed in order toaccommodate different size pizza crusts and different numbers ofparallel paths for the pizza crusts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic flow diagram for the feed paths;

FIG. 2 shows a cut away section of one gear driven pump;

FIG. 3 shows a top view of a part of the production line for dispensingsauce onto a plurality of pizzas; and

FIG. 4 is a flow diagram for the computer sequence.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, a supply tank 10 is shown containing a quantity of material12 which, in the present example, may be tomato sauce for application tothe surface of pizza crusts although it should be understood that thepresent invention may be used in a variety of applications with a numberof other materials.

A feed line 14 is shown emerging from the bottom of the supply tank 10and leading to a pump 16. Pump 16 drives the sauce through a supply line18 to the input port 20 of a plurality of gear driven pumps 21-27connection with FIG. 2, pumps 21-27 are provided with two sections, oneof which contains a pair of gears to drive the sauce through a port tothe other section where it moved downwardly in FIG. 1 through aplurality of outputs 31-37 to a like plurality of electrically actuatedvalves 41-47. It should be understood that while FIG. 1 shows 7pump/valve combinations, this is primarily for ease in the descriptionand in actual practice, any number may be used. It should also be notedthat for food dispensing a non-food contaminating material such asstainless steel is preferred for constructing the pumps and other partsof the system which come in contact with the food.

Each valve may be independently turned "on" and "off" by an electricalinput shown by arrow 50 which is controlled by a micro processor orcomputer better seen in FIG. 3. When "on", the full flow of the saucesupplied by the pumps 21-27 will pass through the valves and will flowdownwardly through supply ports shown by arrows 51-57 in FIG. 1 so as todeposit the sauce onto the surface of a pizza crust 60 passingunderneath. When turned "off", all of the sauce from pumps 21-27 willpass through valves 41-47 to a first return line 62. This constantmotion of the sauce prevents the shear thinning problem of thixotropictype materials. It should be noted that the first return line 62 extendsback to the supply tank 10 and down through the material 12 to aposition near the bottom outlet. The reason for this is to assure thatthe sauce which has just been through the system will be the first usedand thus prevents a build-up of the early or used sauce in tank 10.

It should also be noted that should any of the valves become blocked,the pump associated therewith will continue to pump and the pressurewill build up to "blow" the blockage out. An example of a multipumpapparatus, (although not previously used for food processing, is ahydraulics flow divider supplied by Delta Power Hydraulic Company ofRockford, Ill.

Returning to gears 21-27, it is seen that they are all driven by a shaft66 which extends through the stack 29 and is keyed to the center of eachgear to provide positive drive as will be better seen in connection withFIG. 2. In FIG. 1, shaft 66 is driven by gears 68, 69 and 70 from ashaft 72 driven by a variable speed motor 74 receiving an input shown byarrow 76 which is controlled by the computer to be described inconnection with FIG. 3.

The sauce supplied through input port 20, in addition to flowing throughpumps 21-27 and valves 41-47, flows through the stack and emerges in asecond return line 80. Return line 80 includes a valve 82 which providesa back-pressure, shown by arrow 84, to assure that there is alwayssufficient pressure to cause sauce to fill the pumps 21-27 and valves41-47. After leaving valve 82, the sauce is fed back to the supply tank10 and through the material 12 to near the bottom of the tank 10 toassure it is used first for the next flow around. Approximately 10-20percent of the flow from pump 16 through input port 20 is fed back totank 10 via the second return line 80 even when all of the valves 41-47are "on", and again the constant motion of the sauce helps prevent the"thixotropic" problem.

Referring now to FIG. 2, a gear section for one of the pumps 21-27 isshown comprising a flat slab 90 of material such as stainless steel andcontaining first and second large apertures 92 and 94 sized to providespace for a pair of gears 96 and 98 to rotate. Apertures 92 and 94 areoverlapping so that the teeth, such as shown by reference numerals 102and 104 on gears 96 and 98 respectively, will mesh in the centerportion. It is seen that the upper gear 96 is driven by shaft 66described in connection with FIG. 1 and is keyed as at point 110 to becaused to rotate in a direction shown by arrow 114. Gear 98 is driven bygear 96 to rotate in a direction shown by arrow 116 around a shaft 120.Shaft 120 is only keyed to one of the gears in stack 29 as is shown bydashed line 122 so that the shaft will turn within the bearings asopposed to the gears turning on the shaft. All of the other gears in thestack 29 are mounted to be able to float on shaft 120.

The entrance port 20 is shown in FIG. 2 as an aperture 126 which extendsinto the plane of FIG. 2 and all the way through the stack 29. An exitport is shown by aperture 130 and this extends into the plane of FIG. 2only so far as to join a port in an adjacent slab of material shown bydashed line 132 which extends down to emerge as one of the lines such as31 in FIG. 1 leading to valve 41. It should be understood that each pumpis composed of two slabs of material joined together as by boltsextending through the stack of gears. A final end plate closes the sideof the last element. Apertures such as shown by reference numerals 140are used to accommodate such bolts. In each set of two slabs, the firstone includes an output duct such as 132 in FIG. 2, and the other onecontains the gears like that shown in FIG. 2. The back of the next setof two slabs covers the side of its neighbor to prevent sauce fromflowing out.

It is seen in FIG. 2 that sauce enters the pump through aperture 126, isdriven through the gears 96 and 98 where they mesh and is forced out ofaperture 130 to exit port 31 and to the appropriate valve 41 in FIG. 1.If valve 41 is open, all of the sauce is then deposited on the pizzacrust. It should be noted that other positive displacement pumps may beemployed in place of those shown in FIG. 2, e.g. a G-Rotor Pump.

Referring now to FIG. 3, a top view of a system for depositing sauceonto pizza crusts is shown. A conveyor surface 150, which may be in theform of a belt or mesh is shown passing around rollers 154 and 158. Oneof the rollers, 158 in FIG. 3, is driven by a motor 160 through amechanical linkage shown as dashed line 162. Motor 160 is driven at aspeed set by the magnitude of an input signal shown by arrow 164 from amicro processor or computer 166. The surface 150 is shown driven bymotor 160 in a direction shown by arrow 168 and the speed of surface issensed by a counter 170 connected to roller 154 by a line shown as arrow172. A signal indicative of this speed is sent to micro processor 166via a line shown as arrow 174 and is used by the microprocessor 166 tocontrol the speed of motor 160 and assure that the surface 150 is movingat an exact desired speed.

A plurality of paths for pizza crusts are formed by movable edges orfences 180, 182, 184 and 186 placed by the operator in accordance withthe size of the pizza and the number of channels desired. While threesuch channels are shown, with different sized pizzas or if fewer or morechannels were desired, the channels formed by the fences 180 etc. caneasily be changed.

A plurality of pizza crusts such as shown by reference numerals 190 arefed onto the surface 150 by any conventional means (not shown) and thenthey move with the surface 150 in the channels formed by fences 180 etc.A plurality of detectors, such as optical detectors 192-196 are spacedout across the width of surface 150 and operate to detect the presenceof an oncoming pizza crust at an exact known location. While fivedetectors are shown in FIG. 3, fewer or more may be employed. It shouldbe noted that only three of the five detectors need be used for thethree channels shown in FIG. 3 (i.e. detectors 192, 194 and 195). Theother detectors 193 and 196 would be for use if a different set up withdifferent size pizzas or a different number of channels were employed.It should also be noted that the position of the detectors need not becentered on a channel, as shown, nor need the detectors be evenlyspaced. It is only necessary that the micro processor know the positionof the detectors.

When a detector senses the oncoming pizza crust, it sends a signal tothe micro processor 166 via lines such as shown by arrows 201-205. Themicro processor 166, knowing the speed of the surface and the positionof the pizza crust, sends valve operating signals out via lines such asshown by arrows 210, 212 and 214 to the valves which are shown in FIG. 3as three groups of seven valves in boxes 216, 218 and 220 which aremounted above the moving surface 150. Accordingly, just when the leadingedge of a pizza crust starts to pass under a valve box such as is shownin FIG. 3 by a pizza crust 224 starting under box 220, the valvecentered on the pizza is opened and sauce start to form a strip over thecrust as it moves. Shortly thereafter, the computer opens the two valveson either side of the center one and then the next two so that aplurality of sauce strips are put down in the pattern shown by the darkstrips 230. As the pizza crust starts to leave the area, the computercloses the outer valves, then the next etc. and last, the center valveand valves, to assure that the deposition is as even as possible overthe pizza crust and does not flow onto the conveyor surface. Afterdeposition as strips 230, the sauce tends to flow together to form arelatively uniform surface of sauce and because of the exact control ofthe valves, there is little variation in quantity from one pizza toanother. It has been found that no more than 12% by weight and as littleas 3% variation is found in the application of sauce thus assuring thedesired uniformity.

Micro processor 166 also controls the variable speed drive motors 74 vialines shown as arrows 76 which were described in connection with FIG. 1and these motors operate the pumps through the gear drives shown asdashed lines 240 in FIG. 3.

Micro processor also includes a plurality of operator controlled inputsshown by knobs 260, 262 and 264 providing input signals shown by arrows268, 270 and 272 to micro processor 166. These are representative ofinputs by the operator to inform the micro processor of, for example,the desired speed of the surface 150, the number of channels to be used,the size of the pizza crusts to be sauced, and/or the rate of sauce flowwhich can be controlled by varying the relative speeds of the variablespeed drive 74 and the motor 160.

Micro processor 166 also receives an input from a plurality of outputanalyzing devices 174 which may be optical scanners to detect if thesauce is being put on properly and if not, to alert the operator to theproblem so that it may be corrected at an early point in time. Outputsfrom devices 174 are shown as a line 176 to microprocessor 166. It mayalso be desirable to provide other detectors such as weighing devices(not shown) at points on the surface 150 before and after theapplication of sauce to the pizza crusts. Signals from the weighingdevices would be sent to the microprocessor 166 to provide exactinformation as to the quantity of sauce being applied.

Finally, micro processor 166 is shown having an output represented by anarrow 280 to a memory 282 which operates to store system performanceinformation such as the number of pizzas processed, the size, the amountof sauce and/or any other facts about which the operator would like tobe kept informed. This information may be presented to a display (notshown) via a line shown by arrow 284.

Referring to FIG. 4, a flow diagram, the sequence of operation ofcomputer 166 is shown for one line of oncoming pizza crusts. Similardiagrams would be used for each one of the paths and each would beindependently operated. A detector 300 observing the moving surfacekeeps looking for the pizza and if it is not seen inquires again. Whenit determines that a pizza crust has reached a predetermined position, asignal to a Run Delay Timer box 306 is actuated. Run Delay Timer 306knows the speed of the surface, via connection 174 in FIG. 3, and knowsthe position of the detector 300 with respect to the valves andaccordingly knows the delay necessary before actuating the valves. Atthe determined time, a signal is sent to a Sequential Valve Actuationbox 310 which also knows the speed of the surface and determines theproper sequence for actuating the valves. To this end, an input isprovided via a line 312 which is connectable by a switch mechanism shownschematically by arrow 316 and dashed line 318 to one of a plurality ofmask patterns P1-Pn identified by reference numerals 320-329. Eachpattern provides a signal indicative of a particular sized pizza cruste.g. 6", 8", 10" etc. so that sequential valve 310 can determine thenumber of valves to use and their proper sequence. For example, assume a6" pizza required 7 stripes of sauce to cover the pizza. The sequencer,knowing the speed of the surface would activate valve number 4 in acentral group of seven valves to start depositing the center stripe.Shortly thereafter valves 3 and 5 would be activated followed by 2 and 6and finally 1 and 7 would be activated for a short time. Thereafter,valves 1 and 7 would be deactivated, then 2 and 6, 3 and 5 and finallyvalve 4 as the pizza crust left the area under the valves. At this timea signal to a Cycle Complete box 330 would cause a signal to theDetector 300 to begin the next cycle.

It is thus seen that I have provided an improved dispensing device whichovercomes the problems encountered in the prior art. Although thepresent invention has been described with reference to preferredembodiments, workers skilled in the art will recognize that changes maybe made in form and detail without departing from the spirit and scopeof the invention.

What is claimed is:
 1. Apparatus for dispensing a thixotropic food ontoa food surface comprising:source means for providing a continuous supplyof the thixotropic food; conveyor means for transporting the foodsurface past a dispensing position; a dispensing port mounted above thedispensing position; valve means having "on" and "off" conditions and aninput port and first and second output ports; flow conducting meansconnecting the input port to the source means to receive a supply of thethixotropic food therefrom, the first output port connected to thedispensing port to deposit the thixotropic food on the food surface asit passes through the dispensing position, said flow conducting meansincluding a positive displacement pump means connected to the sourcemeans to move the thixotropic food therefrom to the input port; firstreturn means connected to the second output port and to the source meansto provide a first path to return excess thixotropic food to the sourcemeans and to provide continuous motion of the thixotropic food throughthe valve means; second return means connected to the flow conductingmeans and to the source means to provide a constant second pathindependent from the first path to return excess thixotropic food to thesource means and to provide continuous motion of the thixotropic food inthe flow conducting means, the provision of continuous motion operatingto overcome the thixotropic tendency to resist motion; flow restrictionmeans connected to the second return means to provide a back pressure toassure continuous flow to the valve means; position sensing meansoperable to produce a signal indicative of the position of the foodsurface with respect to the dispensing position; computer means capableof receiving the signal indicative of position and operable to controlthe "on" condition of the valve means in accordance therewith;connecting means to connect the conveyor means to the computer means sothat the speed of the conveyor means is controlled by the computermeans; speed sensing means in communication with the computer means toproduce an output signal indicative of the speed of the conveyor meansand to supply the output signal to the computer means; and food surfaceand thixotropic food sensing means for supplying an output indicative ofthe number of food surfaces and a quantity of thixotropic food andconnecting it to the computer means.
 2. Apparatus according to claim 1further including memory means connected to the computer means to storethe information indicative of the number of food surfaces and thequantity of thixotropic food.
 3. Apparatus for dispensing a thixotropicfood onto a plurality of food surfaces moveable along a plurality oflanes, comprising:source means for providing a continuous supply of thethixotropic food; conveyor means with a variable speed for transportingthe plurality of food surfaces past a first location; a dispensing portmounted above the first location; valve means having an input port andfirst and second output ports, the valve means including at least onevalve for each lane with the dispensing port for each valve beingpositioned above each lane for dispensing thixotropic food when thevalve is in an "on" condition; flow conducting means connecting theinput port to the source means to receive a supply of the thixotropicfood therefrom, the first output port connected to the dispensing portto deposit the thixotropic food on the plurality of food surfaces asthey pass through the first location; first return means connected tothe second output port and to the source means to provide a first pathto return excess thixotropic food to the source means and to providecontinuous motion of the thixotropic food through the valve means; andsecond return means connected to the flow conducting means and to thesource means to provide a constant second path independent from thefirst path to return excess thixotropic food to the source means and toprovide continuous motion of the thixotropic food in the flow conductingmeans, the provision of continuous motion operating to overcome thethixotropic tendency to resist motion; speed detecting means forproducing a signal indicative of the speed of the conveyor; positiondetecting means for producing a signal indicative of the position of thefood surfaces with respect to the dispensing ports; computer meanscapable of receiving the signals indicative of position and speed andoperable to open and close the valve means to control the flow ofthixotropic food from the dispensing ports on to the food surfaces;means for producing a signal indicative of a size of the food surfaces;means for producing a signal indicative of the number of lanes of foodsurfaces on which thixotropic food is to be dispensed; and connectingmeans in communication with the computer means for connecting thecomputer means to receive the signals indicative of the size of thesurfaces and number of lanes so as to modify the operation of the valvesto assure all of the surfaces receive a proper amount of thixotropicfood.
 4. Apparatus according to claim 3 wherein the means for producinga signal indicative of the size of the food surfaces includes aplurality of predetermined pattern masks producing outputs representingpredetermined surface sizes and switch means connecting a selectedpattern mask signal to the valves to adjust the operation of the valvesin accordance with the size of a selected food surface.
 5. Apparatusaccording to claim 4 further including means connecting the computermeans to the conveyor mechanism to control the speed thereof. 6.Apparatus according to claim 5 further including positive displacementpump means connected between the source means and the valves to providecontinuous flow of thixotropic food thereto.
 7. Apparatus according toclaim 6 further including back pressure means for applying a backpressure to the thixotropic food in the pump means to assure that asufficient quantity of thixotropic food is supplied to the valves.
 8. Adispensing system for applying thixotropic food onto food surfacescomprising a plurality of orifices connected through a plurality ofvalves to a source of thixotropic food, a variable speed conveyormechanism for moving food surfaces in one or more lanes under theorifices, detector means producing an output indicative of the positionof a food surface with respect to the orifices, speed detecting meansfor producing a signal indicative of the speed of the conveyor mechanismand computer means receiving the signals indicative of position andspeed and operable through a valve actuator to open and close the valvesto control the flow of thixotropic food from the orifices onto the foodsurface, comprising:means for producing a signal indicative of a size ofthe food surfaces; means for producing a signal indicative of the numberof lanes of food surfaces on which thixotropic food is to be dispensed;and means connecting the computer means to receive the signalsindicative of size and lanes and to modify the operation of the valvesto assure all of the food surfaces receive the proper amount ofthixotropic food.
 9. Apparatus according to claim 8 wherein the meansfor producing a signal indicative of the size of the food surfacesincludes a plurality of predetermined pattern masks producing outputsrepresenting predetermined surface sizes and switch means connecting aselected pattern mask signal to the valves to adjust the operation ofthe valves in accordance with a selected food surface size. 10.Apparatus according to claim 8 further including means connecting thecomputer means to the conveyor mechanism to control the speed thereof.11. Apparatus according to claim 8 further including positivedisplacement pump means connected between the source of thixotropic foodand the valves to provide continuous flow of thixotropic food thereto.12. Apparatus according to claim 11 further including back pressuremeans for applying a back pressure to the thixotropic food in the pumpmeans to assure that a sufficient quantity of thixotropic food issupplied to the valves.
 13. Apparatus for dispensing a thixotropic foodonto a plurality of food surfaces arranged to move under a dispensingposition and to assure continuous motion of the thixotropic food toprevent flow change due to the thixotropic property of the thixotropicfood comprising:positive displacement pump means connected to a supplyof thixotropic food to move the thixotropic food therefrom to a firstoutput; valve means having "on" and "off" conditions and an inputconnected to the first output to receive the thixotropic food, the valvehaving a dispensing port located at the dispensing position to depositthixotropic food onto a food surface thereunder when the valve is in the"on" condition and the valve having a first return port connected toreturn thixotropic food to the supply when the valve is in the "off"condition to assure continuous motion of the thixotropic food and asecond return port connected between the output and the supply toconstantly return thixotropic food to the supply independently from thefirst return means when the valves are in both the "on" condition and"off" condition to further assure continuous motion of the thixotropicfood, wherein the second return port includes flow restriction means toprovide a back pressure to assure continuous flow to the valve means;conveyor means operable to move the food surface to the dispensingposition; position sensing means operable to produce a signal indicativeof the position of the food surface with respect to the dispensingposition; computer means capable of receiving the signal indicative ofposition and operable to control the "on" condition of the valve meansin accordance therewith; connecting means connecting the conveyor meansto the computer means so that the speed of the conveyor means iscontrolled by the computer means; speed sensing means in communicationwith the computer means to produce an output signal indicative of thespeed of the conveyor means and to supply the output signal to thecomputer means; and food surface and thixotropic food sensing means forsupplying an output signal indicative of the number of food surfaces andthe quantity of thixotropic food and connecting it to the computermeans.
 14. Apparatus according to claim 13 further including memorymeans connected to the computer means to store the informationindicative of the number of food surfaces and the quantity ofthixotropic food.